Created
March 15, 2026 01:08
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Issue #480 investigation scripts: root-only DispatchSource watcher vs recursive FSEvents
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| import Foundation | |
| import Dispatch | |
| let fileManager = FileManager.default | |
| let rootURL = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true) | |
| .appendingPathComponent("latest-watch-test-\(UUID().uuidString)", isDirectory: true) | |
| let nestedURL = rootURL.appendingPathComponent("Browsers", isDirectory: true) | |
| try fileManager.createDirectory(at: nestedURL, withIntermediateDirectories: true) | |
| defer { try? fileManager.removeItem(at: rootURL) } | |
| let descriptor = open((rootURL as NSURL).fileSystemRepresentation, O_EVTONLY) | |
| guard descriptor != -1 else { | |
| fputs("failed to open root directory\n", stderr) | |
| exit(1) | |
| } | |
| enum Phase { | |
| case nested | |
| case root | |
| } | |
| var phase = Phase.nested | |
| var nestedTriggered = false | |
| var rootTriggered = false | |
| let done = DispatchGroup() | |
| done.enter() | |
| let source = DispatchSource.makeFileSystemObjectSource(fileDescriptor: descriptor, eventMask: .write, queue: .global()) | |
| source.setEventHandler { | |
| switch phase { | |
| case .nested: | |
| nestedTriggered = true | |
| case .root: | |
| rootTriggered = true | |
| } | |
| } | |
| source.setCancelHandler { | |
| close(descriptor) | |
| } | |
| source.activate() | |
| func waitForEvent(seconds: TimeInterval) { | |
| let deadline = Date().addingTimeInterval(seconds) | |
| while Date() < deadline { | |
| usleep(50_000) | |
| } | |
| } | |
| DispatchQueue.global().asyncAfter(deadline: .now() + 0.5) { | |
| let nestedFile = nestedURL.appendingPathComponent("Firefox.txt") | |
| fileManager.createFile(atPath: nestedFile.path, contents: Data("test".utf8)) | |
| waitForEvent(seconds: 1.0) | |
| phase = .root | |
| let rootFile = rootURL.appendingPathComponent("top-level.txt") | |
| fileManager.createFile(atPath: rootFile.path, contents: Data("test".utf8)) | |
| waitForEvent(seconds: 1.0) | |
| source.cancel() | |
| done.leave() | |
| } | |
| done.wait() | |
| print("nested_change_triggered=\(nestedTriggered)") | |
| print("root_change_triggered=\(rootTriggered)") |
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| import Foundation | |
| import CoreServices | |
| final class Watcher { | |
| private var stream: FSEventStreamRef? | |
| private let callback: ([String]) -> Void | |
| init(path: String, callback: @escaping ([String]) -> Void) { | |
| self.callback = callback | |
| var context = FSEventStreamContext( | |
| version: 0, | |
| info: UnsafeMutableRawPointer(Unmanaged.passUnretained(self).toOpaque()), | |
| retain: nil, | |
| release: nil, | |
| copyDescription: nil | |
| ) | |
| let flags = UInt32(kFSEventStreamCreateFlagUseCFTypes | kFSEventStreamCreateFlagFileEvents) | |
| stream = FSEventStreamCreate(nil, { _, info, _, pathsPointer, _, _ in | |
| let watcher = Unmanaged<Watcher>.fromOpaque(info!).takeUnretainedValue() | |
| let paths = unsafeBitCast(pathsPointer, to: CFArray.self) as! [String] | |
| watcher.callback(paths) | |
| }, &context, [path] as CFArray, FSEventStreamEventId(kFSEventStreamEventIdSinceNow), 0.1, flags) | |
| FSEventStreamSetDispatchQueue(stream!, .global()) | |
| FSEventStreamStart(stream!) | |
| } | |
| deinit { | |
| if let stream { | |
| FSEventStreamStop(stream) | |
| FSEventStreamInvalidate(stream) | |
| FSEventStreamRelease(stream) | |
| } | |
| } | |
| } | |
| let fileManager = FileManager.default | |
| let rootURL = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true) | |
| .appendingPathComponent("fsevent-test-\(UUID().uuidString)", isDirectory: true) | |
| let nestedURL = rootURL.appendingPathComponent("sub", isDirectory: true) | |
| try fileManager.createDirectory(at: nestedURL, withIntermediateDirectories: true) | |
| defer { try? fileManager.removeItem(at: rootURL) } | |
| let semaphore = DispatchSemaphore(value: 0) | |
| let watcher = Watcher(path: rootURL.path) { paths in | |
| print("paths=\(paths)") | |
| semaphore.signal() | |
| } | |
| DispatchQueue.global().asyncAfter(deadline: .now() + 0.5) { | |
| let nestedFile = nestedURL.appendingPathComponent("a.txt") | |
| fileManager.createFile(atPath: nestedFile.path, contents: Data()) | |
| } | |
| let result = semaphore.wait(timeout: .now() + 3.0) | |
| print(result == .success ? "event" : "timeout") | |
| _ = watcher |
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